Summary
Mechanisms underlying loss of consciousness following propofol administration remain incompletely understood. The objective of this study was to compare frontal lobe electroencephalography activity and brainstem reflexes during intravenous induction of general anaesthesia, in patients receiving a typical bolus dose (fast infusion) of propofol compared with a slower infusion rate. We sought to determine whether brainstem suppression (‘bottom‐up’) predominates over loss of cortical function (‘top‐down’). Sixteen ASA physical status‐1 patients were randomly assigned to either a fast or slow propofol infusion group. Loss of consciousness and brainstem reflexes were assessed every 30 s by a neurologist blinded to treatment allocation. We performed a multitaper spectral analysis of all electroencephalography data obtained from each participant. Brainstem reflexes were present in all eight patients in the slow infusion group, while being absent in all patients in the fast infusion group, at the moment of loss of consciousness (p = 0.010). An increase in alpha band power was observed before loss of consciousness only in participants allocated to the slow infusion group. Alpha band power emerged several minutes after the loss of consciousness in participants allocated to the fast infusion group. Our results show a predominance of ‘bottom‐up’ mechanisms during fast infusion rates and ‘top‐down’ mechanisms during slow infusion rates. The underlying mechanisms by which propofol induces loss of consciousness are potentially influenced by the speed of infusion.
Brain–computer interfaces (BCIs), also known as brain–machine interfaces (BMIs), are a group of experimental procedures in which an external sensor is used to provide information about a specific brain process in order to change the measured quantity. A BCI acquires signals from the brain of a human or an animal using any one or more of these sensors, then selects or extracts specific features of interest from the signal and converts and then translates these into artificial output that can act on the body or the outside world. A BCI may influence human performance by replacing, restoring, supplementing, or enhancing brain function. In this chapter, we discuss the extant research in terms of experimental work and neuroscience understanding of the application of BCIs and neurofeedback systems in influencing human performance in different brain functions, namely, action, perception, cognition, and emotion, in healthy individuals, expert performers, and patients.
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